The present invention relates to a computer system suitable for adaptation to, for example, a notebook type portable computer. More particularly, this invention relates to a computer system equipped with a computer and an expansion unit to and from which the computer body is attachable and detachable.
The entire contents of Japanese Patent Application No. 8-44920 filed on Mar. 1, 1996 are incorporated herein by reference.
Recently, various kinds of laptop type or notebook type personal portable computers which are easy to carry around and operable on a battery are developed such type of portable computer is generally designed to be attached to an expansion unit as needed for functional expansion.
This expansion unit has a drive bay for receiving a drive unit like a hard disk drive and expansion slots to install various kinds of option cards. Therefore, connecting a portable computer to this expansion unit as needed can easily expand the functions of that portable computer without degrading the portability of the portable computer.
A new concept called hot docking has recently been introduced. This "hot docking" can permit a peripheral device such as a CD-ROM drive to be added or unstalled while the system is in operation. Various operating systems support this hot docking function.
In connecting a portable computer to the aforementioned expansion unit, the bus in the expansion unit is connected to the bus in the portable computer. When both buses are connected while the bus cycle is being executed, therefore, it is very likely that both the portable computer and the expansion unit malfunction due to a transient phenomenon or the like. This necessitates that the connection should be made while both machines are powered off.
There is a system which has a switch on the bus of a portable computer to control the connection to the bus of an expansion unit so that both buses can be connected while the system is in operation. However, this system actually connects both buses while the bus cycle of the bus on the portable computer side is idling or until it becomes unaffected by a transient phenomenon when the switch is set on.
While an expansion unit is important to expand the functions of a portable computer, the prior art prevents the connection of the bus of the portable computer to the bus of the expansion unit while the bus cycle of the bus of the portable computer is being executed.